Funny true story rather than joke, heard at a fairly remote airport in 'North Britain'. They'd just got a brand spanking new tower, to replace the aged wartime one. When the old one was demolished Mr contractor had to take away its septic tank as well. Come the day when the concrete covers came off Mr c phones the management 'you'd better come and see this, it's full of johnnies'. Management 'mystified', but sporting knowing look as final piece of a jigsaw puzzle from many years before falls into place!